Field of the Invention
This invention relates to clinical, medical and laboratory equipment and supplies and more particularly relates to elastomeric closures for vials and other containers adapted to admit passage of liquid transfer implements such as pipettes and tips of oral syringes into the container for drawing doses of liquids held therein, in particular for dosing of pharmaceutical medications.
State of the Prior Art
Many elastomeric closures have been conceived for the aforedescribed purpose. Known elastomeric closures include those which are initially closed and are torn open by force of an implement tip as well as those which are pre-cut with slits of various configurations to facilitate passage and entry of the implement tip. A common difficulty with prior art elastomeric closures of this type has been that the closure encompasses and grips the liquid transfer implement to form an air tight seal which prevents interior air pressure from equilibrating with ambient air pressure. As liquid is drawn from the container a vacuum is created which limits the liquid flow into the transfer implement, and may pull fluid out of the implement as the implement is withdrawn from the container. In prior closures various measures have been taken to provide air passages and vents, through the elastomeric closure or otherwise, to facilitate equilibration of internal and ambient air pressures.